Out there question is your power switch on the psu or a board connection if it’s the board connection can you bypass the switch to turn it on? Is it possible you have a duff switch?

bartonxp wrote on 2024-04-12, 00:49:

Was there any proof that it was ever working? A claim that something was 'tested working' has little merit these days. Maybe it never worked to begin with, evidence in this thread seems to suggest it.

I've never had I working, so I can't prove that I did work. Just the fadding hope that it's not completly dead. Because then I'd need to buy a new motherboard and hope that it worked.

Greywolf1 wrote on 2024-04-12, 11:26:

Out there question is your power switch on the psu or a board connection if it’s the board connection can you bypass the switch to turn it on? Is it possible you have a duff switch?

It's a switch that's connected to the motherboard. I have also tried the classic screwdriver touching the pins method.

I’ve had a read through the manual for the motherboard you listed if you have the same manual read page 19 about the usb wake-up function it mentions that your computer won’t switch on if you have the wrong jumper setting if you have a non compatible psu for this function.
Also there is a LED inbetween the 4th and 5th pci slot is it lit when on power.
Your motherboard also has a chassis intrusion function but I don’t know how that works
Some other mentions also does the board work with nothing connected like drives ,ram, cpu should beep like crazy with error codes 🤣
Check jumper settings for your cpu or any test spares.

Hope this gives you some new venues if head scratching good luck with further diagnosis.

Matrolisk wrote on 2024-04-10, 21:42:

You were right, I had done the test wrong. I redid the previous tests making sure to place the red probe on the bare tinned par […]
Show full quote

You were right, I had done the test wrong. I redid the previous tests making sure to place the red probe on the bare tinned part.

Results With No CPU
CPU V_core - 1
V_dimm - 1

Results With CPU
CPU V_core - 23.4-24.2
V_dimm - Started at about 120 a went up 188 where it stayed.

OK, that's more inline with the resistances I expected.
Fortunately, neither the CPU V_core nor RAM V_dimm rails are shorted.
Unfortunately, that still leaves us a problem to find.

Here's a test to try: what happens if you plug the PSU to the motherboard and manually put a wire bridge between the PS_ON and a ground/COM pin on the ATX connector? Does the motherboard stay turned On? Or does the PSU shut down immediately again. The former would suggest something is wrong with the CMOS logic for the front panel header on the motherboard. The latter would suggest a short-circuit is still lingering somewhere.

In the years of repairing motherboards, I've seen some strange "one-of-a-kind" issues that are certainly worth checking for, since they aren't actually too uncommon.
One of these is shorted / mashed in pins in any of the USB ports or headers... or even other ports that have power going to them (VGA output, for example.) Normally, most motherboards have thermal fuses for all of the headers and rear ports. But I've encountered an issue with one motherboard (a s939 MSI) where the thermal/poly-fuse wouldn't react very quickly, making the PSU twitch and turn Off first before the fuse opened. Through experimentation, I found that the board would eventually turn On (once the poly-fuse got hot and opened up), and especially with less-sensitive PSUs. The issue was a VGA port on the mobo was pulled out, and some of the pins inside the port were shorting to ground (including the 5V line.) Hence why my mobo didn't want to start. I've also seen this issue on a motherboard with mashed in pins in the USB port. Removing / pulling out the shorted pins from the USB port fixed that issue.

But anyways... do the test suggested above by bridging the PS_ON pin on the ATX connector (usually a green-colored wire on a standard ATX connector) to ground. Then we can see where to hunt from there. IIRC, I also just remembered that some Asus motherboards have had issues with weak pull-up/down logic... so if the mobo is unable to pull the PS_ON signal low, that could also be causing this issue... which is what the above test should reveal if true or not.

I did the test.

The first time I did it the PSU remained on, the motherboard did nothing.

Every time afterwards the PSU only stayed on for a second. Longer if I kept the pins bridged.

I tried turning the PSU off and on multiple times to see if I could get the first result again but it never happened.

Board is dead. Was this board from Ebay ? Did the seller have a high + % (like 99%) ? Just curious.
Me thinks you bought a dead board. Also are you sure the cpu works ?

Matrolisk wrote on 2024-04-14, 03:52:

I did the test.

The first time I did it the PSU remained on, the motherboard did nothing.

OK, good... to a point - means nothing is badly shorted, at least.
The not-so-good part is that problems like these tend to be harder to find, since it's more likely to be a small component on a signal line that is bad (rather than a power component) that is causing the rest of the system to halt.

Matrolisk wrote on 2024-04-14, 03:52:

Every time afterwards the PSU only stayed on for a second. Longer if I kept the pins bridged.

I tried turning the PSU off and on multiple times to see if I could get the first result again but it never happened.

In that case, unplug the PSU and try a CMOS reset. Then, plug the PSU in the board and again bridge PS_ON to ground manually. Only this time, also press the power button about 1 second after the PSU turns On.
Let's see if that makes the mobo POST. Some motherboards have a "weird" power-up sequence and won't necessarily POST, even if you give them power from the PSU.
Also, if you get the PSU to turn On, what voltage do you get at pin #8 on the ATX connector? (This is the PG / Power Good pin.)

So I reset the cmos according to the manual then the the test to power the motherboard. The PSU did not stay on. Still tried the power button press but nothing happened.
I did however have the cpu and gpu fan would spin up for the brief time the psu was on for.